clippy_lints/src/double_parens.rs

   1 use crate::utils::span_lint;
   2 use rustc::declare_lint_pass;
   3 use rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
   4 use rustc_session::declare_tool_lint;
   5 use syntax::ast::*;
   6
   7 declare_clippy_lint! {
   8     /// **What it does:** Checks for unnecessary double parentheses.
   9     ///
  10     /// **Why is this bad?** This makes code harder to read and might indicate a
  11     /// mistake.
  12     ///
  13     /// **Known problems:** None.
  14     ///
  15     /// **Example:**
  16     /// ```rust
  17     /// # fn foo(bar: usize) {}
  18     /// ((0));
  19     /// foo((0));
  20     /// ((1, 2));
  21     /// ```
  22     pub DOUBLE_PARENS,
  23     complexity,
  24     "Warn on unnecessary double parentheses"
  25 }
  26
  27 declare_lint_pass!(DoubleParens => [DOUBLE_PARENS]);
  28
  29 impl EarlyLintPass for DoubleParens {
  30     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
  31         if expr.span.from_expansion() {
  32             return;
  33         }
  34
  35         match expr.kind {
  36             ExprKind::Paren(ref in_paren) => match in_paren.kind {
  37                 ExprKind::Paren(_) | ExprKind::Tup(_) => {
  38                     span_lint(
  39                         cx,
  40                         DOUBLE_PARENS,
  41                         expr.span,
  42                         "Consider removing unnecessary double parentheses",
  43                     );
  44                 },
  45                 _ => {},
  46             },
  47             ExprKind::Call(_, ref params) => {
  48                 if params.len() == 1 {
  49                     let param = &params[0];
  50                     if let ExprKind::Paren(_) = param.kind {
  51                         span_lint(
  52                             cx,
  53                             DOUBLE_PARENS,
  54                             param.span,
  55                             "Consider removing unnecessary double parentheses",
  56                         );
  57                     }
  58                 }
  59             },
  60             ExprKind::MethodCall(_, ref params) => {
  61                 if params.len() == 2 {
  62                     let param = &params[1];
  63                     if let ExprKind::Paren(_) = param.kind {
  64                         span_lint(
  65                             cx,
  66                             DOUBLE_PARENS,
  67                             param.span,
  68                             "Consider removing unnecessary double parentheses",
  69                         );
  70                     }
  71                 }
  72             },
  73             _ => {},
  74         }
  75     }
  76 }